1. Field of the Invention
The invention is related to the field of magnetic recording and, in particular, to the manufacture of a read head having a relatively narrow track width such that the data storage capabilities of magnetic disk drive systems may be increased.
2. Statement of the Problem
Magnetic disk drive systems are used in a variety of electrical devices for mass storage of information. The disk drive systems include a magnetic media disk and an assembly of write and read heads. The assembly of write and read heads is supported by a slider that is mounted on a suspension arm. The suspension arm biases the slider toward the magnetic media disk. When the magnetic media disk rotates, air flow generated by the rotation of the disk causes the slider to fly on a cushion of air at a very low elevation (fly height) over the disk. When the slider rides on the air, the actuator moves the suspension arm to position the write and read heads over selected data tracks on the magnetic media disk. The write and read heads write data to and read data from, respectively, data tracks on the magnetic media disk. Processing circuitry connected to the write and read heads then operates according to a computer program to implement writing and reading functions.
To construct the read head, a plurality of sensor layers are deposited across the surface of a substrate. A photolithographic process is then conducted such that an ion milling mask is “imaged” above the sensor layers to establish a magnetic read track width for the read head. An ion milling process then removes unmasked portions of the sensor layers to define the track width of the read head.
In order to achieve greater data storage density on the magnetic media, magnetic data bits are written in increasingly smaller sizes. The read heads are therefore fabricated with a reduced track width to properly read the smaller sized data bits. A reactive ion etching (RIE) process is used to “image” a pattern in a photo resist layer onto an ion mill hard mask. Then, the hard mask is ion milled to pattern the hard mask image into the sensor. A problem with this process exists with the limitation of the lithography tool that is used to produce the track-width of the read head. At relatively small dimensions, not enough photo resist material remains to effectively image transfer the photo resist onto the hard mask. Even if the image transfer step is successful, the combined thickness of the imaging layer and the hard mask results in a relatively high aspect ratio that causes “shadowing” effects in the structure. These shadowing effects cause tapering at the foot of the sensor after milling. The tapering makes the read head less effective due to the changing geometry. That is, a read head is more effective at reading data on a magnetic disk when its geometries are perpendicular, or square, with respect to the disk. Additionally, the structure tends to form “dips” adjacent to the sensor after hard bias deposition that make CMP (chemical mechanical polishing) less effective in removing extraneous materials.